Zero Emissions Reciprocating Pump

ABSTRACT

A sealing system for a pump includes a housing having an internal chamber adapted to receive a portion of a plunger. A primary seal is translatable within the chamber in sealing relation with the housing. The primary seal includes first and second elastomeric members adapted to sealingly engage the plunger. The first and second elastomeric members are spaced apart from one another a distance greater than or equal to a maximum stroke of the plunger. A secondary seal is spaced apart from the primary seal and adapted to sealingly engage the plunger. A chamber contains a barrier fluid in contact with the primary seal and the secondary seal. A pressurizing device maintains a pressure of barrier fluid at a magnitude greater than a peak pressure of a fluid pumped by the plunger such that the pumped fluid is restricted from entering the barrier fluid chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/729,439 filed on Mar. 28, 2007. The entire disclosure of theabove application is incorporated herein by reference.

BACKGROUND

The present disclosure generally relates to pumping systems and, moreparticularly, to a sealing arrangement for a pumping system.

Pumping systems have been used to pump petroleum and petro-chemicalproducts at pumping well installations for some time. Other pumpingsystems have been utilized to transfer fluids where spills and leaksfrom the pumping system may contaminate the environment. Reducing oreliminating environmental contamination is a primary concern formanufacturers of these pumping systems.

One pumping system manufacturer has provided a stuffing box sealassembly including a first seal and a second seal separated by anenvironmentally safe fluid-filled inner chamber. The first sealseparates the inner chamber from the atmosphere while the second sealseparates the inner chamber from the fluid being pumped. The sacrificialenvironmentally safe fluid is stored in a reservoir and transmitted tothe inner chamber. The inner chamber pressure varies throughout thepumping operation but remains at a slightly higher pressure than thefluid being pumped. While this system has reduced environmentalcontamination, a need exists for an improved sealing arrangement forpumping systems.

SUMMARY

A sealing system for a pump having a plunger includes a housing havingan internal chamber adapted to receive a portion of the plunger. Aprimary seal is axially translatable within the internal chamber and insealing relation with the housing. The primary seal includes first andsecond elastomeric members adapted to sealingly engage the plunger. Thefirst and second elastomeric members are spaced apart from one another adistance greater than or equal to a maximum stroke of the plunger. Asecondary seal is located within the internal chamber and adapted tosealingly engage the plunger. The secondary seal is spaced apart fromthe primary seal. A barrier fluid chamber contains a barrier fluid incontact with the primary seal and the secondary seal. A pressurizingdevice maintains a pressure of barrier fluid at a magnitude greater thana peak pressure of a fluid pumped by the plunger such that the pumpedfluid is restricted from entering the barrier fluid chamber.

A sealing system for a pump having a reciprocating plunger is alsodisclosed. The system includes a housing having an internal chamberadapted to receive a portion of the plunger. A primary seal ispositioned within the internal chamber in sealing relation with thehousing and includes first and second elastomeric members adapted tosealingly engage the plunger, the first and second elastomeric membersbeing spaced apart from one another by an axially moveable sleeve adistance greater than or equal to a maximum stroke of the plunger. Asecondary seal is located within the internal chamber and adapted tosealingly engage the plunger. The secondary seal is spaced apart fromthe primary seal. A barrier fluid chamber contains a barrier fluid andis defined by the second elastomeric member and the secondary seal. Apressurizing device maintains a pressure of the barrier fluid at amagnitude greater than a peak pressure of a fluid pumped by the plungersuch that the pumped fluid is restricted from entering the barrier fluidchamber.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a partially sectioned plan view of an exemplary power pumpequipped with a sealing system constructed in accordance with theteachings of the present disclosure;

FIG. 2 is a cross-sectional side view of the power pump depicted in FIG.1;

FIG. 3 is a fragmentary side view of the power pump showing an enlargedview of the stuffing box;

FIG. 4 is a hydraulic schematic representing the sealing system for thepower pump;

FIG. 5 is a cross-sectional side view of a pressurizing device of thesealing system shown in FIG. 4; and

FIG. 6 is a fragmentary side view of an alternate stuffing box.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

An exemplary power pump 10 is depicted in FIGS. 1 and 2. Power pump 10is a reciprocating piston type pump having first, second and thirdplunger assemblies 12, 14, 16 driven by a power source 18. Each plunger12, 14, 16 includes a suction port 20, 22, 24 and a discharge port 26,28, 30, respectively. Plungers 12, 14, 16 are substantially similar toone another. Accordingly, power pump 10 will be described in detail onlyin relation to plunger 16.

Power pump 10 includes a drive unit 40, a reciprocating plunger 42, astuffing box 44 and a fluid cylinder 46. Plunger 42 is coupled to driveunit 40 for axial reciprocating motion within fluid cylinder 46 andstuffing box 44. Plunger 42 is moveable between an extended position anda retracted position. FIG. 2 illustrates plunger 42 at a partiallyextended position. Movement of plunger 42 from the extended position tothe retracted position causes pumped fluid to enter suction port 24.During retraction of plunger 42 a suction valve 48 opens to allow pumpedfluid to enter a central cavity 50 formed within fluid cylinder 46.Plunger 42 is also in communication with central cavity 50. A dischargevalve 52 is positioned between central cavity 50 and discharge port 30.During the retraction stroke, discharge valve 52 is closed. When thedirection of travel of plunger 42 is reversed to cause plunger 42 tomove from the retracted position toward the extended position, suctionvalve 48 closes while plunger 42 is driven into central cavity 50. Fluidpreviously positioned with central cavity 50 is pressurized. Dischargevalve 52 opens to allow the pressurized pumped fluid to exit dischargeport 30.

Drive unit 40 includes a crankcase 60 rotatably supporting a crankshaft62. A gear train 64 drivingly interconnects crankshaft 62 to powersource 18. Gear train 64 includes an input shaft 66 rotatably supportedin a gear housing 68. Input shaft 66 includes a drive gear 70 rotatablyfixed thereto. A driven gear 72 is in meshed engagement with drive gear70. Driven gear 72 is fixed for rotation with crankshaft 62.Accordingly, torque input provided by power source 18 rotates inputshaft 66 which in turn rotates drive gear 70, driven gear 72 andcrankshaft 62.

A first end 73 of a connecting rod 74 is rotatably coupled to a journal76 formed on crankshaft 62. Journal 76 has a center offset from an axisof rotation of crankshaft 62 such that journal 76 follows an eccentricpath upon rotation of camshaft 62. A second end 78 of connecting rod 74is rotatably coupled to a cross head 80. Cross head 80 is slidablyreceived within a bore 82 formed in crankcase 60. A first end 84 ofplunger 42 is fixed to cross head 80. As such, rotation of crankshaft 62causes reciprocating linear motion of cross head 80 and plunger 42.

Stuffing box 44 interconnects drive unit 40 and fluid cylinder 46.Stuffing box 44 includes a cylinder 100 in receipt of a portion ofplunger 42. Within cylinder 100, plunger 42 is shaped as a cylinderhaving an outer surface 102 with a substantially constant outerdiameter. Stuffing box 44 functions to guide plunger 42 along a desiredpath while preventing pumped fluid positioned within fluid cylinder 46from escaping to the environment. Stuffing box 44 also performs thefunctions of providing a lubricant to outer surface 102 to reduce wearbetween plunger 42 and the seals surrounding the plunger.

In particular, stuffing box 44 includes a primary seal 104, a secondaryseal 106 and tertiary seal 108 positioned within cylinder 100 incommunication with plunger 42. A throat bushing 110 is inserted at oneend of cylinder 100 and is sized to guide plunger 42 along its axis oftranslation. A threaded retainer 112 is fixed to the opposite end ofcylinder 100 and functions to retain secondary seal 106 and tertiaryseal 108 within a counterbore 114 formed within cylinder 100.

Primary seal 104 includes three “V” rings 116, captured between a firstend plate 118 and a second end plate 120. Each of the components ofprimary seal 104 are axially moveable within a bore 122 formed incylinder 100. A spring 124 imparts a predetermined compressive load onprimary seal 104 in the static state. As will be described in greaterdetail, primary seal 104 is maintained in axial compression by spring124 during pump operation.

Secondary seal 106 and tertiary seal 108 are mounted within a casing 130retained within counterbore 114 by a ring 132. Casing 130 includes aninternal groove 134 in receipt of secondary seal 106. Secondary seal 106may be constructed as a multi-component seal having an O-ring 136bottomed within groove 134 and a wiper 138 positioned in engagement withouter surface 102 of plunger 42. O-ring 136 acts as a spring to biasedlyengage wiper 138 with plunger 42. It should be appreciated that thesecondary seal may be constructed as a one-piece elastomer or may havean alternative form. For example, secondary seal 106 may be equippedwith a single or multiple lips in contact with outer surface 102 withoutdeparting from the scope of the present disclosure. Tertiary seal 108 isconstructed from an elastomer and positioned within a groove 139 formedwithin casing 130. Tertiary seal 108 engages outer surface 102 ofplunger 42.

First and second outer grooves 140, 142 are formed in casing 130. Afirst outer o-ring 144 is positioned within groove 140 and a secondouter o-ring 146 is positioned within outer groove 142. O-rings 144, 146are placed in biased engagement with counterbore 114 to prevent fluidpassage between casing 130 and cylinder 100. A plurality of passageways148 radially extend through casing 130 in communication with an outergroove 150 formed on casing 130. Outer groove 150 is aligned with aleakage port 152 radially extending through cylinder 100. An inlet port154 also radially extends through cylinder 100. Inlet port 154communicates with a barrier fluid cavity 156 in receipt of spring 124.An environmentally safe barrier fluid is provided to barrier fluidcavity 156.

FIG. 4 depicts a hydraulic schematic of a sealing system 180 constructedin accordance with the teachings of the present disclosure. Sealingsystem 180 includes stuffing box 44, a pressure referencing device 182and a pressurizing device 184. Sealing system 180 is operable to providepressurized barrier fluid to barrier fluid cavity 156 at a pressureconsistently exceeding the peak discharge pressure of power pump 10. Oneskilled in the art will appreciate that based on the reciprocatingnature and multiple piston arrangement previously defined in relation topower pump 10, the discharge pressure provided by power pump 10 pulsatesbetween a low pressure value and a high pressure value for each cycle ofplunger 42. Furthermore, depending on the physical characteristics ofthe fluid being pumped, such as viscosity and temperature among others,the magnitude of the high pressure may vary over time. The highestpressure reached during pumping is referred to as the peak pressure.

Sealing system 180 includes a first line 186 plumbed in communicationwith discharge ports 26, 28, 30 from each of plungers 12, 14, 16.Accordingly, a pulsating discharge pressure signal is provided to aninlet 188 of pressure referencing device 182. Pressure referencingdevice 182 is operable to output and maintain the peak pressure sensedat inlet 188 to an outlet 190. Pressure referencing device 182 includesa one-way check valve 192 positioned in a first fluid branch 194. Aspressure is provided to inlet 188 from the discharge of power pump 10,one-way check valve 192 operates to maintain the peak pressure at outlet190. Fluid is allowed to flow to outlet 190 through one-way check valve192 when pressure within line 186 is greater than the pressure at outlet190. Flow in the reverse direction is restricted.

Pressure referencing device 182 includes a second fluid branch 196positioned in parallel with first fluid branch 194. A differentialpressure valve 198 is plumbed within second fluid branch 196.Differential pressure valve 198 normally remains closed. However, when apredetermined pressure differential exists across valve 198, it opens toallow fluid to pass from the pump discharge to outlet 190. Pressuredifferential valve 198 is provided to account for a condition where aninsufficient quantity of fluid is positioned in a line 200interconnecting outlet 190 and pressurizing device 184. This conditionmay occur when the discharge pressure reduces a relatively large amount.

As shown in FIG. 5, pressurized fluid within line 200 acts on a firstsurface 202 of a piston 204 positioned within a housing 206 ofpressurizing device 184. Barrier fluid is located on an opposite face208 of piston 204. A pipe 210 is fixed to housing 206. Barrier fluid isallowed to pass through an aperture 212 formed in a plate 214 located atthe intersection between pipe 210 and housing 206. A tube 216 is fixedto piston 204. Tube 216 extends through aperture 212 such that a portionof tube 216 is located within housing 206 and another portion is locatedwithin pipe 210.

First and second springs 218, 220, are captured between plate 214 and astop 222 fixed to the distal end of tube 216. Springs 218, 220 apply aforce to piston 204 to assure that the pressure of the barrier fluid isalways greater than the peak pressure provided from the pump discharge.This is accomplished by pre-loading springs 218, 220 to apply a force topiston 204 regardless of its axial position. In one example, thepressure of the barrier fluid acting on surface 208 of piston 204exceeds the peak pressure on surface 202 of piston 204 by at least onebar. It is contemplated that tube 216 is axially moveable betweenretracted and extended positions. At the retracted position, springs218, 220 are fully compressed and the pressure of the barrier fluid isapproximately two bar greater than the pressure acting on surface 202.At the fully extended position of tube 216, springs 218, 220 are attheir fully extended position and the pressure of the barrier fluid isone bar greater than the pressure acting on surface 202 of piston 204.It should be appreciated that the 1 bar to 2 bar pressure range ismerely exemplary and other pressure increase ranges may be implemented.Furthermore, while the spring arrangement within pressurizing device 184provides a simple mechanical method for providing increased outputpressure, other pressurizing devices may be used without department fromthe scope of the present disclosure.

Pressurized barrier fluid exits pressurizing device 184 at an outlet240. A line 242 provides pressurized barrier fluid to inlet port 154 ofstuffing box 44. A fill port 244 may be provided in line 242 to allow auser to add barrier fluid to the system. A barrier fluid level detectionsystem may optionally be employed to inform a user of sealing system 180to the location of piston 204 and a possible need to add barrier fluidto the system. A magnetic ring 250 is fixed to tube 216 and translatesas piston 204 translates. A position indicator 252 senses the axialposition of magnetic ring 250 and outputs a signal indicative of themagnetic ring's position. The axial position of magnetic ring 250correlates to the position of piston 204 and how close the piston 204may be to bottoming out against plate 214. Barrier fluid may be added inresponse to the position signal to assure this condition does not occur.

Operation of power pump 10 and sealing system 180 will now be described.Power source 18 provides torque to gear train 64 to rotate crankshaft62. Connecting rod 74 and cross head 80 cooperate to axially displaceplunger 42. As plunger 42 is moved from its retracted position towardits extended position during a pressurized fluid discharge stroke, apressure differential across primary seal 104 is relatively low. Morespecifically, the pressure within central cavity 50 is at or near themaximum pressure magnitude of the discharged fluid. In addition, aspreviously mentioned, the pressure of the barrier fluid within barrierfluid cavity 156 is slightly greater than the peak discharge pressure.Accordingly, V-rings 116 are relatively relaxed. A thin film of barrierfluid adheres to plunger 42 and travels from barrier fluid cavity 156into engagement with the components of primary seal 104 to lubricate theseal and charge the spaces between V-rings 116 with barrier fluid.Furthermore, because the pressure of the barrier fluid is greater thanthe peak pressure found within central cavity 50, any leakage of fluidthat may occur involves flow of barrier fluid into the pumped fluid.Pumped fluid is not allowed to travel toward the more highly pressurizedbarrier fluid cavity 156. Based on this mode of operation, a barrierfluid is selected to exhibit properties that do not adversely affect theperformance characteristics of the pumped fluid.

During the pressurized fluid discharge stroke previously described, arelatively large pressure differential exists across secondary seal 106because leakage port 152 is maintained at atmospheric pressure. Due tothe relatively large pressure differential, barrier fluid within barrierfluid cavity 156 may leak across secondary seal 106 through passageway148, groove 150, leakage port 152 and into a collection tank 260. Aspreviously mentioned, barrier fluid is an environmentally friendly fluidand a controlled and collected leak of this type of fluid does not raiseenvironmental concerns.

Tertiary seal 108 acts as a wiper and operates in relatively cleanconditions with relatively low differential pressure. Tertiary seal 108functions to prevent leakage of the barrier fluid to atmosphere and toretain leaked fluid within passageway 148 and collection tank 260.

Continued rotation of crankshaft 62 causes plunger 42 to move from theextended position toward its retracted position during a suction stroke.The pressure within central cavity 50 is substantially lower than thepressure within barrier fluid cavity 156 during the suction stroke. Atthe same time, a relatively high differential pressure exists acrossprimary seal 104 to cause V-rings 116 to compress. The compressedV-rings more tightly engage outer surface 102 of plunger 42. Thecombination of an energized primary seal 104, a relatively highdifferential pressure between barrier fluid cavity 156 and centralcavity 50 and also the pre-charging of spaces between V-rings 116 withbarrier fluid ensures that no pumped fluid will be carried into barrierfluid cavity 156. A cycle of discharge stroke and subsequent suctionstroke is repeated as crankshaft 62 rotates.

FIG. 4 depicts an optional recharging circuit 280 operable to transferleaked barrier fluid positioned within collection tank 260 into usewithin barrier fluid cavity 156. Recharging circuit 280 includes aninlet line 282 in communication with collection tank 260. Collected andpreviously leaked barrier fluid is drawn from collection tank 260 with apump 284. Output from pump 284 is provided to inlet port 154 orsomewhere along line 242. In this manner, power pump 10 and sealingsystem 180 may be left unattended for longer periods of time withoutrequiring additional barrier fluid to be added.

With reference to FIG. 6, an alternate stuffing box is depicted atreference numeral 300. Stuffing box 300 may be used within a sealingsystem substantially similar to sealing system 180 in lieu of stuffingbox 44. Stuffing box 300 includes a cylinder 302 in receipt of a portionof plunger 42. As previously mentioned, plunger 42 includes asubstantially constant outer diameter having an outer cylindricalsurface 102.

Stuffing box 300 includes a primary seal 304, a secondary seal 306 and atertiary seal 308 positioned within cylinder 302 in sealing engagementwith outer surface 102. A throat bushing 310 is positioned at a firstend 312 of cylinder 302. A bore 314 extends through throat bushing 310and is sized to guide plunger 42 along its axis of translation. Athreaded retainer 316 is fixed to an opposite end 318 of cylinder 302and functions to retain secondary seal 306 and tertiary seal 308 withina counterbore 320 formed within cylinder 302.

Primary seal 304 includes a first elastomeric member or V-ring 324, asleeve or bushing 326 and a second elastomeric member or V-ring 328captured between a first end plate 330 and a second end plate 332. Eachof the components of primary seal 304 are axially moveable within a bore336 formed in cylinder 302. A spring 338 provides a predeterminedcompressive load to primary seal 304. Spring 338 also applies acompressive load to a third end plate 339 and secondary seal 306. Aspreviously described in relation to stuffing box 44, the components ofprimary seal 304 and secondary seal 306 remain in axial compressionduring pump operation.

Second V-ring 328 and secondary seal 306 define a cavity 340. An inletport 342 is in communication with cavity 340 and provides a fluidpassage for highly pressurized barrier fluid to enter cylinder 302.Second V-ring 328 and secondary seal 306 function to retain the barrierfluid within cavity 340. The pressure within cavity 340 acts on secondend plate 332, second V-ring 328, third end plate 339 and secondary seal306. The force supplied by the pressurized fluid, as well as the forceprovided by spring 338, is translated through bushing 326 to firstV-ring 324. Spring 338 provides a self-adjustment mechanism for primaryseal 304 and secondary seal 306.

First V-ring 324 is axially spaced apart from second V-ring 328 adistance substantially equal to or greater than the maximum allowablestroke of plunger 42. Based on this relative positioning, portions ofplunger 42 that are exposed to pumped fluid are prevented from axiallytravelling into a cavity 340 defined by second V-ring 328 and secondaryseal 306. This sealing arrangement prevents the transport of pumpedfluid that may collect within microscopic pores of plunger 42 intocavity 340. The remainder of stuffing box 300 is substantially similarto stuffing box 44 and a detailed description of each component will notfollow. It should be appreciated, however, that the multiple elementsecondary seal 106 and multiple element tertiary seal 108 may bereplaced by singular, monolithic (V) rings as depicted in FIG. 6.

In operation, plunger 42 is moved from a retracted position toward anextended position during a pressurized fluid discharge stroke. At thistime, a pressure differential across primary seal 304 is relatively low.As was previously described in relation to stuffing box 44, some barrierfluid passes by second V-ring 328. A thin film of barrier fluid adheresto plunger 42 and travels from cavity 340 across second V-ring 328 andalong a portion of surface 102 lying between first V-ring 324 and secondV-ring 328. This flow of barrier fluid acts to wash plunger 42 and moveany pumped fluid that may be positioned between first V-ring 324 andsecond V-ring 328 toward first end 312 of cylinder 302. The washingoperation in combination with the spacing of first V-ring 324 fromsecond V-ring 328 restricts and substantially eliminates the entry ofpumped fluid into cavity 340. The integrity of the barrier fluid ismaintained. The functions of secondary seal 306 and tertiary seal 308are substantially similar to those previously described in relation tostuffing box 44.

As plunger 42 is moved from the extended position toward its retractedposition during a suction stroke, a relatively high differentialpressure exists across primary seal 304. Spring 338 and the pressure ofthe barrier fluid within cavity 340 causes second V-ring 328 and firstV-ring 324 to compress. The compressed V-rings tightly engage outersurface 102 of plunger 42. Barrier fluid is now found not only withincavity 340 but also between first V-ring 324 and second V-ring 328. Thetightly engaged V-rings, the relatively high differential pressurebetween barrier fluid cavity 340 and first end 312, and the pre-chargingof any voids that may be present between first V-ring 324, bushing 326and second V-ring 328 with barrier fluid, ensures that no pumped fluidwill be carried into cavity 340.

Furthermore, the foregoing discussion discloses and describes merelyexemplary embodiments of the present disclosure. One skilled in the artwill readily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationsmay be made therein without departing from the spirit and scope of thedisclosure as defined in the following claims.

1. A sealing system for a pump having a plunger, comprising: a housinghaving an internal chamber adapted to receive a portion of the plunger;a primary seal within the internal chamber and in sealing relation withthe housing, the primary seal including first and second elastomericmembers adapted to sealingly engage the plunger, the first and secondelastomeric members being spaced apart from one another a distancegreater than or equal to a maximum stroke of the plunger; a secondaryseal located within the internal chamber and adapted to sealingly engagethe plunger, the secondary seal being spaced apart from the primaryseal; a barrier fluid chamber containing a barrier fluid in contact withthe primary seal and the secondary seal; and a pressurizing device tomaintain a pressure of the barrier fluid at a magnitude greater than apeak pressure of a fluid pumped by the plunger such that the pumpedfluid is restricted from entering the barrier fluid chamber.
 2. Thesealing system of claim 1 wherein the primary seal is axiallytranslatable within the internal chamber and further includes an axiallytranslatable bushing adapted to surround the plunger and transfer a loadbetween the first and second elastomeric members.
 3. The sealing systemof claim 2 further including a spring applying a compressive force tothe first elastomeric member, the bushing, the second elastomeric memberand the secondary seal.
 4. The sealing system of claim 3 wherein thespring is positioned within the barrier fluid chamber.
 5. The sealingsystem of claim 1 further including a tertiary seal being positionedwithin the internal chamber and adapted to engage the plunger at alocation further from the primary seal than the secondary seal and aleakage port extending through the housing in communication with aportion of the internal chamber between the secondary and the tertiaryseals.
 6. The sealing system of claim 5 further including a collectiontank in communication with the leakage port for receipt of barrier fluidthat has leaked past the secondary seal.
 7. The sealing system of claim5 wherein the primary, secondary and tertiary seals each include aninner diameter sized to engage a plunger having a constant diameteralong its length.
 8. The sealing system of claim 1 further including abarrier fluid level indicator operable to output a signal indicative ofthe level of barrier fluid within the sealing system.
 9. The sealingsystem of claim 1 further including a pressure referencing device beingin communication with the pumped fluid and outputting fluid at apressure magnitude equal to a peak pressure of the pumped fluid to thepressurizing device.
 10. The sealing system of claim 1 further includinga recharging circuit including a pump drawing fluid from a collectiontank in receipt of barrier fluid that has previously leaked past thesecondary seal, the pump reintroducing the previously leaked barrierfluid into the barrier fluid chamber.
 11. A sealing system for a pumphaving a reciprocating plunger, comprising: a housing having an internalchamber adapted to receive a portion of the plunger; a primary sealpositioned within the internal chamber in sealing relation with thehousing and including first and second elastomeric members adapted tosealingly engage the plunger, the first and second elastomeric membersbeing spaced apart from one another by an axially moveable sleeve adistance greater than or equal to a maximum stroke of the plunger; asecondary seal located within the internal chamber and adapted tosealingly engage the plunger, the secondary seal being spaced apart fromthe primary seal; a barrier fluid chamber containing a barrier fluid andbeing defined by the second elastomeric member and the secondary seal;and a pressurizing device to maintain a pressure of the barrier fluid ata magnitude greater than a peak pressure of a fluid pumped by theplunger such that the pumped fluid is restricted from entering thebarrier fluid chamber.
 12. The sealing system of claim 11 furtherincluding a spring applying a compressive load to the first elastomericmember via the sleeve and second elastomeric member.
 13. The sealingsystem of claim 12 wherein the spring is positioned within the barrierfluid chamber.
 14. The sealing system of claim 11 wherein the first andsecond elastomeric members are axially moveable within the internalchamber.
 15. The sealing system of claim 11 further including acollection tank in communication with the leakage port for receipt ofbarrier fluid that has leaked past the secondary seal.
 16. The sealingsystem of claim 11 wherein the first and second elastomeric membersinclude V-rings.
 17. The sealing system of claim 11 wherein the firstelastomeric member is oriented to restrict flow of pumped fluid towardthe second elastomeric member.
 18. The sealing system of claim 17wherein the second elastomeric member is oriented to restrict flow ofbarrier fluid toward the first elastomeric member.
 19. The sealingsystem of claim 11 wherein a radial clearance exists between the sleeveand the housing as well as between the sleeve and the plunger.